1. Field of the Invention
The present invention relates to an internal combustion engine mounted, for example, on an automobile and more particularly to a control system for a direct injection internal combustion engine.
2. Description of the Related Art
Today, from a viewpoint of environmental protection, it is required to reduce such substances as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) contained in the gas emitted by automobiles. Direct injection engines have been developed to reduce such substances contained in emission gas. In a direct injection engine, fuel is injected from each injector directly into the combustion chamber of each engine cylinder, so that diameters of fuel particles emitted form the injector are reduced to promote fuel combustion and thereby reduce emission gas substances and increase the engine output power.
To reduce the diameters of fuel particles emitted from an injector, it is necessary to pressurize the fuel. Hence, various techniques to realize a high pressure fuel supply system have been proposed.
According to the technique described in JP-A No. 2007-23930, for example, a pressure accumulation type fuel injection control system which is provided with a pressure accumulating container for accumulating pressurized fuel to achieve stable fuel combustion and engine performance, injectors for injecting the high pressure fuel in the pressure accumulating container into the cylinders of the engine, and a fuel supply pump for pressurizing the sucked-in fuel and feeding the pressurized fuel to the pressure accumulating container and in which discharging of the fuel from the fuel supply pump to the pressure accumulating container is adjusted to achieve a target common rail pressure comprises: a pressure pattern estimation unit for estimating a fuel pressure transition in the pressure accumulating chamber during an injection period determined based on a requested injection quantity and a target common rail pressure; a surplus pressure range calculation unit for calculating, with the target common rail pressure determined based on pressure pattern data generated by the pressure pattern estimation unit, a pressure range where the pressure pattern data during the injection period exceeds the target common rail pressure; and a pressure reduction valve for controlledly releasing the common rail pressure to a low pressure side so as to remove the surplus pressure range calculated by the surplus pressure range calculation unit.
According to the technique described in JP-A No. 2007-327409, a fuel supply system for an internal combustion engine is provided with: a casing for reducing noise generated when fuel is pressure-transferred, the casing having an internal pressure chamber, a fuel inlet and a fuel outlet; a metering valve for opening and closing the fuel inlet; a biasing member for biasing the metering valve in the direction for opening the fuel inlet; a solenoid for providing the metering valve with an attractive force in the direction for closing the fuel inlet; a plunger which can, by reciprocating interlocked with a crankshaft, suck fuel into the pressure chamber and pressurize and pressure-transfer the sucked-in fuel; and a solenoid control unit for controlling the solenoid according to the operating condition of the internal combustion engine, the solenoid control unit determining the magnitude of the attractive force with which the solenoid provides the metering valve according to the fluid force of the fuel applied to the metering valve.